X-RAY MICKOSCOPY 



smallest blood and lymphatic vessels in 

 either the dead or living animal. In the vas- 

 cular field of human embryology and anat- 

 omy its future is assured. 



The magnified images of unstained animal 

 and human tissues, both soft and miner- 

 alized, exhibit much useful histological and 

 cytological information. Stereoscopic visuali- 

 zation of internal structure and the inter- 

 pretation of differences in absorption open 

 new avenues to the microscopist. 



The x-ray projection microscope lends it- 

 self to spatial localization and chemical de- 

 termination on a microscopic scale. By 

 utilizing the initial x-ray magnification, and 

 applying the known laws of x-ray absorption 

 and fluorescence, the intense x-ray point 

 source afforded by the instrument offers as 

 yet unrealized possibilities for the micro- 

 chemical analysis of tissue areas but a few 

 microns in diameter. 



REFERENCES 



1. Lamarque, p., Radiol., 27, 563 (1936). 



2. Engstrom, a., In "Analytical Cytology," 



McGraw-Hill, New York, 1955. 



3. Hancox, N. M., Exptl. Cell Research, 13, 263 



(1957). 



4. Saunders, R. L. de C. H. and van der Zwan, 



L., Proc. 2nd International Symp. X-ray 

 Microscopy and Microanalysis, Stockholm, 

 1959. 



R. L. DE C. H. Saunders 



INTER-RELATION OF TECHNIQUES FOR THE 

 INVESTIGATION OF MATERIALS 



The fullest advantages are obtained from 

 the use of microradiography when the results 

 are associated with data or information de- 

 rived from other sources such as the optical 

 microscope, x-ray diffraction, etc. (1,2). The 

 diagram is intended to show how several 

 different techniques are interrelated and help 

 in various ways to build up reasonably com- 

 plete understanding of the constitution and 

 texture of materials. The scheme is perhaps 

 particularly applicable to metallurgical and 



mineralogical samples, but has a more gen- 

 eral interest. Techniques to the left of the 

 diagram give the chemical analysis and indi- 

 cate phases present, and those to the right 

 give information about segregation effects 

 and texture, but may also contribute to the 

 identification of phases. Special x-ray tech- 

 niques which give information about pre- 

 ferred orientation have been omitted in the 

 interests of simplicity, while the identifica- 

 tion of single crystals by x-rays (or other 

 techniques) is probably outside the present 

 terms of reference. 



Chemical analysis and x-ray (powder) 

 diffraction of bulk samples to establish the 

 general chemical composition and phase 

 constitution are often the first steps in a 

 comprehensive investigation of a material. 

 For the other techniques it is desirable to 

 prepare thin sections cut from lump mate- 

 rial and if it is intended to examine both, it 

 is desirable to examine the same area of solid 

 surface from which the thin section has been 

 taken, and if possible to use the same thin 

 section for optical examination as for micro- 

 radiography. As the diagram implies, the use 

 of a pohshed surface of a lump of material 

 by reflection microscopy is characteristic of 

 practice with metallurgical specimens and 

 thin section microscopy is more typical of 

 petrological examination. The examination 

 of rocks, ceramics or other materials by re- 

 flection microscopy is not excluded. The 

 electron microscope is indicated for either 

 technique, but in fact transmission is most 

 frequently employed. Foils or other thin 

 specimens are generally used, or otherwise 

 solid surfaces are represented by replicas. 

 The scale of magnification in microradiog- 

 raphy is, however, comparable to that of 

 the optical microscope. 



The diagram draws attention to a number 

 of other points. For example, microradiog- 

 raphy may contribute confirmatory evidence 

 or even in certain circumstances provide the 

 main evidence for the identity of certain 

 phases and give information about grain 



586 



